1. Field
The method and system herein relates to communication systems, and more specifically to a method and system for determining the position of a mobile station based upon base station identification and a repeater discriminant.
2. Related Art
The communications field requires accurate position information in many instances for mobile stations (MSs) such as cellular telephones, personal communication system (PCS) devices, and other user equipment (UE). Global Positioning Systems (GPS) offer an approach to providing wireless MS position determination. These systems employ satellite vehicles (SVs) in orbit around the earth. A GPS user can derive precise navigation information including three-dimensional position, velocity and time of day through information gained from the SVs.
An example of a wireless position location system is an MS with a GPS receiver, communicating with one or more base stations (BSs) in communication with a core communication network. The MS also communicates with a position determination module (PDM), also referred to as a position determination entity (PDE), that provides an estimated position of the MS and SV signal acquisition assistance data to the MS, among other functions. Typically signal acquisition assistance data is derived from the PDM's best understanding of where the MS is currently located and the MS clock state at that time.
One way in which the PDM determines a location estimate for the MS is through network-based range measurements. Network-based range measurements, also known as pilot phase measurements (PPMs), or advanced forward link trilateration (AFLT) measurements in IS-95 and IS-2000 communication networks, are range measurements to a cell tower antenna. Range measurements can be useful in determining a reasonably accurate position and clock state for the MS. It is possible, however, that range measurements are skewed by signal time delay encountered at a repeater located in the transmission path between a base station and MS used to amplify signals transmitted in both the forward and reverse links. This time delay may, for example, delay PDM location algorithms from converging on a position solution, produce an error in position solution, or prevent the PDM from arriving at a position solution.
Regardless of whether MS position is determined through range measurements, global positioning, or a combination of both, position solutions can be especially difficult or impossible when the MS is located within a structure, for example, a building made of concrete, steel and low-emissivity glass, a tunnel, within a canyon, or the like, due to the difficulty in receiving and transmitting an adequate number of range signals or receiving positioning signals from a global positioning system. Even with a repeater located at or near the structure, obtaining a position solution for a MS located within the structure may be difficult.
A need exists for a method and system that improves position solutions for mobile stations located within a structure, for mobile stations having difficulty in receiving and transmitting ranging signals, or for receiving positioning signals from a global positioning system.